The view through Britain's uPVC windows has gone a little cloudy.
About £2bn is spent replacing seven million windows every year in the UK as homeowners rush to install plastic frames they hope will be easier to maintain than the older wood and metal ones.
Early uPVC windows were prone to yellow rapidly
But environmental pressure groups are deeply concerned by the 200,000 tonnes of waste already generated every year by discarded uPVC or wooden windows from UK homes and are calling for a change in attitude.
Ninety per cent of the waste, they say, goes direct to landfill sites.
New building rules
Groups like Greenpeace are strongly opposed to the use of uPVC plastic material, arguing that it leads to the release of poisonous chemicals.
However, new UK Government rules which require all new windows to use thick double-glazed units have made uPVC the only affordable option for many homeowners.
Traditional slim and elegant wooden sash window designs are not strong enough to hold the new hi-tech heavy glass.
Though the new glass can be contained in thicker timber frames, it is generally a much more expensive option.
Greenpeace believes these timber frames are best and it is also opposed to the option of aluminium framed double-glazing because of the large amounts of energy consumed in obtaining and manufacturing the metal.
Tackling heat loss
Ironically, the new government rules on double-glazing were put in place to try to assist with another environmental problem: the high heat loss from Britain's homes which drives up energy consumption.
However, the UK Government-funded body English Heritage argues the insistence on sealed-unit double-glazing is a flawed strategy.
According to some industry reports, 40% of these new units are failing within five years and English Heritage believes energy saving targets could be met instead by better roof insulation and draught-proofing of existing windows.
Metal frames have also fallen out of fashion
Indeed, English Heritage recommends that homeowners only remove original wood windows if they are completely rotten.
The organisation says repair is the best long-term option as the timber installed 100 years ago was usually high-quality wood from natural forests, in contrast to the less durable heat-treated farmed timber that can be bought today.
Even traditional Victorian terraced houses must comply with the double-glazing rule for any replacement window.
Only the small number of homes in conservation areas are exempt.
Current trends indicate that windows being installed now will be replaced in about 10 years.
This transformation of windows into a "disposable" item contrasts with the attitude of homeowners 100 years ago when windows were carefully maintained and would last as long as the building itself.
The uPVC industry responds to criticism by arguing that its latest products can last 40 years if they are regularly cleaned with the appropriate detergent, and the mechanisms are kept well oiled.
The industry also says the problem of uPVC yellowing over time in sunlight has been removed by new additives to the PVC.
On the recycling issue, the European PVC industry says it aims to recycle up to 75% of old uPVC products by 2010, although it is not clear exactly where the recycled PVC would go.
The British Plastics Federation says many independent authorities have concluded that uPVC is safe in manufacture, use and disposal.